Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$223.77	5.500%	$236.0774	$236.08	$236.10	$236.10
Purchase #2	$58.28	12.417%	$65.5166	$65.52	$65.50	$65.50
Purchase #3	$55.47	10.314%	$61.1912	$61.19	$61.20	$61.20
Purchase #4	$156.93	7.346%	$168.4581	$168.46	$168.45	$168.50
Purchase #5	$120.83	5.211%	$127.1265	$127.13	$127.15	$127.10
Purchase #6	$206.93	10.653%	$228.9743	$228.97	$228.95	$229.00
Purchase #7	$119.61	12.348%	$134.3794	$134.38	$134.40	$134.40
7 purchase totals =	$941.82		$1,021.7235	$1,021.73	$1,021.75	$1,021.80